This invention relates to a wet disc brake assembly having a first stage for reducing the clearance between the discs and a second stage for applying force to the discs to increase the braking torque.
Wet disc brake assemblies are used in vehicles such as lift trucks, front-end loaders and in other devices. Each brake assembly has a disc pack that includes two sets of discs that rotate relative to one another. One set of discs is coupled to a stationary housing, and the other set of discs is coupled to a rotatable member attached to a wheel or some other driven member.
When the brakes are applied by a vehicle operator, a hydraulic piston forces the discs together to increase the friction between them thereby decreasing the relative speed between the sets of discs and slowing the driven member. Typically, clearance must be provided between the discs to minimize parasitic losses resulting from friction between the discs when the brakes are not applied.
More hydraulic fluid is required with greater clearance between the discs. Further, since the piston must travel farther with greater clearance between the discs is used, the brake-apply times inevitably increase.
Therefore, it is desirable to provide a wet disc brake assembly that has a clearance between the discs that results in minimal friction when the brakes are not applied while avoiding increases in the amount of hydraulic fluid necessary or brake-apply times.